Preheat a grill to medium (if you are using a charcoal grill, coals are ready when you can hold your hand 5 inches above grill for just 5 to 6 seconds) . Place a piece of chocolate on each of 10 graham crackers; set aside. Press each marshmallow onto the tip of a skewer. Cook marshmallows, turning occasionally, until toasted to desired doneness.
Using a fork, push each marshmallow onto a chocolate-covered graham cracker. Sandwich with remaining graham crackers. Serve immediately.